This invention relates to a palatal expander and particularly a dual-joint palatal expander to expand upper jaw bone effectively and quickly for accommodating and aligning the front teeth of a patient.
Because of oral disorder or disease, there are cases in which patients, particularly children of young age, need surgical or plastic operation to cut through the palatal or upper jaw bone and gum. After surgical operation, the upper jaw bone need to be expanded for accommodating and aligning the front teeth. Hence a palatal expander is usually employed to expand the upper jaw bone sideward and forward to create more space for the front teeth to grow and align properly.
FIG 1 shows a conventional palatal expander 6 which is also known as jackscrew mounted in the upper jaw of the patient. It has a pair of spaced anchor blocks 62 which have respectively an opposite internal screw bore engageable with a screw bar 64. The anchor blocks 62 are slidable movable along two spaced guide rods 63 which run through the anchor blocks 62. Each anchor block 62 has one side attached to a pair of brackets 61 which have one end fastened to a first upper barrel band 11 and a second upper barrel band 21. The first and second barrel bands 11 and 21 are mounted respectively on a molar 1 and a premolar 2. There is a wire anchor 30 on each barrel band and a steel wire 3 to fasten the first and second barrel bands 11 and 21 together. Turning a screw head 641 located between the anchor blocks 62, the screw bar 64 will be turned and drives the anchor blocks 62 away from each other. The brackets 61 will then push the barrel bands 11 and 21 of two sides away from each other. As the molar 1 and premolar 2 have relatively strong root deeply planted in the upper jaw bone, the upper jaw bone will be stretched and expanded. FIG. 2 shows what is actually happening when using the jackscrew 6 shown in FIG. 1. The upper jaw bone at the front teeth position will be stretched in two opposite directions A and B sideward and slightly backward against a center O and forming a fan angle xcex1. The stretch direction A and B is not linear. Instead of expanding the upper jaw bone sideward and forward, the upper jaw bone will be expanded sideward but crowed backward. The direction of front teeth expansion is unpredictable. This will cause the misalignment of the front teeth. Then an orthodontic treatment is needed to align the front teeth. This adds more pain and trouble to the patients.
FIG 3 shows another conventional palatal expander 6xe2x80x2 also known as a fan-type jackscrew. The operation principle is generally same as the one shown in FIG. 1. However instead of a pair of anchor blocks 62 and guide rods 63, a pair of rocker arms 65 are used to engage with the screw bar 64xe2x80x2. Each rocker arm 65 has a screw end 642 engaged with the screw bar 64xe2x80x2 and a pivotal center 66 engaged with another rocker arm 65. Turning the screw head 641xe2x80x2, the screw bar 64xe2x80x2 will turn and drive the screw end 642 away from each other. Then the rocker arms 65 will be expanded to a wider angle about the pivotal center 66 to move the bracket 61 to push the barrel bands 11 and 21. As a result, the upper jaw bone may also be expanded. The expanding direction Axe2x80x2 and Bxe2x80x2 (shown in FIG. 4) is also being stretched slightly backward against a center Oxe2x80x2 and forming a fan angle xcex1xe2x80x2. It also has similar disadvantage shown in the FIG. 1 example.
Furthermore the prior arts set forth above are difficult to install and use. It is particularly troublesome for children who generally have not much patience to endure such an ordeal for a long period of time. Most children have great resistance to take this long and painful treatment. Even to those children who take this treatment, the effectiveness will be compromised when proper adjustment is not performed regularly. The treatment takes long time and great cost. All this begs for improvement.
It is an object of this invention to provide a rapid palatal expander that is able to expand upper jaw bone of a patient sideward and forward almost linearly so that the upper jaw bone will be stretched horizontally and forward to accommodate the front teeth and growing alignment.
It is another object of this invention to provide a rapid palatal expander that can expand upper jaw bone of a patient effectively and quickly so that total treatment time may be shortened to relieve patient""s trouble and inconvenience and to reduce expense.
It is a further object of this invention to provide a rapid palatal expander that has a constant expansion feature that enables the upper jaw bone of a patient be stretched as desired constantly and automatically without patient""s active involvement or extra efforts. It may further speed up total treatment time and save medical expense.
In one aspect, the palatal expander according to this invention includes a dual-joint fan-type jackscrew. A pair of rocker arms each has one end respectively engaged with a fulcrum and another end engageable with a screw bar. Turning the screw bar, the rocker arms will be moved away sideward in opposite direction to stretch the upper jaw bone sideward and forward. The two fulcrums may be spaced from each other to enable the sideward movement of the rocker arms become almost a linear path. The backward stretching that happened to a single joint fan-type jackscrew thus may be minimized.
In another aspect, this invention provides an elastic means which has two ends engageable with molars of the upper and lower jaw. When patients mouth is closed, the elastic means will be compressed by the upper and lower jaw and produces a forward force to push the upper jaw bone forward.
This may be done without patient""s additional effort, during day time and even in sleep. The jaw bone expanding effect is thus greatly enhanced. It may further shorten total treatment time and may also save the patient a lot of trouble and medical expense.